Environmental, biological, and psychosocial factors can all separately influence the disease burden in asthma. As yet, no studies have taken into account all three categories of factors together, to examine their relative contributions to the disease burden and investigate whether their cumulative effects can explain the health disparities of at-risk populations, either additively or synergistically. Asthma is an ideal chronic condition in which to delineate the potential linkages among biological mechanisms, social factors, and physical environments and, more specifically, to show how these linkages may lead to health disparities. Study Hypotheses: 1) There are socioeconomic status (SES) differentials in the disease burden of asthma; 2) Environmental, biological, and psychosocial factors are linked to the asthma disease burden additively, if not synergistically; and 3) The variance in SES differentials of disease burden will be substantially explained by modeling that takes specific environmental, biological, and psychosocial factors into account. Methods: This proposed study will make use of an established panel of 590 adults with asthma of varying severity. We propose to supplement these survey data with 500 home site visits in which we will directly gather environmental, biological, and psychosocial data. Specific environmental risk factors we will quantify include: allergen sensitization, home allergens, ETS exposure, and indoor air quality. We will also assess perceived stress and social support. In addition, we will link subjects to other potential exposures through external data sets. We will also administer a follow-up survey to investigate the combined influence of environmental, biological, and psychosocial exposures in explaining SES disparities in the disease burden of asthma. This study combines a multidisciplinary team of researchers with expertise in clinical medicine, social sciences, epidemiology, psychology, endocrinology, asthma treatment and prevention, and biostatistics. Anticipated Results and Significance: The proposed investigation will have sufficient power to detect differences in the proportions of outcomes between two groups in the range of 10-15 percent at the 0.05 level for dichotomous outcomes. This project addresses a major research need and can be a basis for the development of public policies to address environmentally related and other health disparities in adult asthma.